Surface Layer Of Specimens Research Articles

Transmission electron microscopic study of the surface layer of surgical resected disc specimens in human temporomandibular joint.

In this study, we investigated specific and characteristic findings of the surface layer of surgical resected disc specimens in human temporomandibular joint osteoarthritis cases by transmission electron microscopy (TEM).Specimens were surgically removed from the TMJ of 5 cases (4 female patients: 5 cases) clinically osteoarthritis. Following findings were observed by TEM. Images were photographed on a JEM1400-Flash Electron microscope (JEOL, Japan) equipped with an EM-14661FLASH high-sensitivity digital complementary metal-oxide-semiconductor camera.Following findings were observed by TEM. 1) The surface is covered with plump fibroblastic and histiocytoid cells. 2) Collagen fiber bundles and collagenous matrix are exposed onto the eroded disc surface. 3) Fibrinous dense material is observed on the eroded disc surface. 4) Bundles of collagen fibers are densely observed. 5) Collagen bundles are rich around capillary vessels. 6) Synovial surface cells reveal features of activated macrophages with vacuole formation. Especially, plump fibroblastic and histiocytoid cells, and activated macrophages with vacuole, which were significant findings of the surface layer. These findings might have a significant effect on the regulation of synovial fluid.

Improvement of Fatigue Strength and Wear Resistance of Molybdenum Diffusion-Bonded Alloyed Steel by Sinter-cold-forging and Vacuum Carbonitriding Processes

This study aims to obtain the superior mechanical properties of Mo diffusion-bonded alloyed steel by the optimum combination of processes: primary-sintering (PS), cold-forging (CF), heat treatment (HT) and shotblast. In our previous research, it was found that the fracture of sintering connections, namely, micro-cracks occurred on the surface layer of high-density specimens in addition to the work hardening on materials, which decreased both the impact energy and the bending strength. Also, since the optimum heat treatment leads the diffusion bonding of the pressurized cracks in the surface layer, the microstructure could be reformed. In this study, it was found that the 0.4 mass%Mo-steel powder had both the highest densification and deformability among the powders of 0.4, 1, 2 and 4 mass%Mo without precipitation of the unneeded ternary molybdenum carbide Fe3Mo3C. Also, when sintered specimens were cold-forged, the impact waveform of those showed clearly effects of both the work hardening and the damage of the microstructure. Finally, both the superior fatigue strength and the wear resistance were implemented with the proper processes to 0.4 mass%Mo sintered steel such as a second sintering, vacuum carbonitriding heat treatment and shotblast. Obtained properties were equal to or more than those of wrought steel SCr420H.

Deicer Salt-Scaling Resistance of Concrete Using Recycled Concrete Aggregates Pretreated by Silica Fume Slurry.

Concrete wastes such as recycled concrete aggregates (RCA) make up a significant part of construction and demolition waste (C&DW) which can be used to minimize usage of natural aggregates and reduce carbon footprint. This paper studies the salt-scaling resistance of recycled aggregate concrete produced with pretreated RCAs. The test method for evaluating salt-scaling resistance in concrete according to DIN EN 1340: 2003 was performed. Four series of concrete mixes using natural aggregates, RCAs, manually pretreated RCA, and modified RCA in a desiccator were subjected to the different tests in terms of bulk electrical resistance in two directions (X and Y) before and after freeze-thaw cycles, ultrasonic pulse velocity, and weight loss of the surface layer of concrete specimens. Moreover, Scanning Electron Microscopy (SEM) of mixes was conducted and the microstructure of mixes considering the interface transition zone was studied. Results show that after exposure to cycles of freezing and thawing, the quality of concrete regarding ultrasonic pulse velocity did not change. The electrical resistance of specimens decreased significantly in X-direction and slightly in Y-direction after applying freeze-thaw cycles in all mixes. Nevertheless, surface modification of RCAs can increase electrical resistance and improve durability of concrete. SEM images show that the interface transition zone before and after freeze-thaw cycles remained unchanged which means strong bond between aggregate, new mortar, and old mortar. An estimation of the total charge passed indicated that all recycled aggregate concretes can be classified in a safe area and with very low chloride ion penetrability according to ASTM C1202.

Surface microstructure evolution mechanism of WC-Co hard alloy treated by high current pulsed electron beam

The surface of WC-Co hard alloy was modified treatment by high current pulsed electron beam (HCPEB). The surface microstructure evolution mechanism of WC-Co hard alloy was characterized by XRD, SEM, EBSD, and TEM, respectively. The temperature distribution of WC-Co hard alloy during HCPEB treatment process was calculated and discussed. The results show that rapid melting and rapid solidification induced by HCPEB caused the phase transformation and the microstructure evolution on the surface of the hard alloy, and when irradiation times was 13th times, the microcracks and voids on the WC-Co hard alloy surface were gradually healed by remelting repeatedly, causing the formation of dense nanostructures. The microhardness of the modified specimen surface layer by 13th irradiation increased to 1159.0 HV, and the wear resistance increased to 1.72 times that of the matrix. The strength and wear resistance of the surface layer of the specimen were improved due to the refinement of WC grains, the forming of WC1-X nanophase, and the precipitation of nanographite particles. The microstructure evolution mechanism on the alloy surface after the modified treatment was proposed that a metastable equilibrium system was formed (WC + WC1-X + Co3W9C4+graphite phase).

A new MAX phases-based electroconductive coating for high-temperature oxidizing environment

In the paper, results of variations of structure, oxidation resistance, and electrical conductivity of novel MAX-phase composite coating are presented. The characteristics of highly dense Ti-Al-C composite bulks and vacuum-arc deposited 6 μm thick coatings before and after heating at 600 °C in air for 1000 h were compared. High electrical conductivity (σ = 1.3·106 S/m) of the highly resistant toward oxidation (Δm/S = 0.07 mg/cm2) Ti-Al-C coating was preserved after long-term heating in air. It was found that the specimen surface layers of MAX-phases Ti3AlC2 and Ti2AlC based bulks and chromium-containing Crofer 22APU steel became semiconductors because of high-temperature long-term oxidation (at 600 °C). The vacuum-arc deposited Ti-Al-C composite coating revealed high oxidation resistance and electrical conductivity along with good mechanical characteristics, namely nanohardness H(10mN) = 9.5 ± 1.5 GPa, and Young’s modulus E = 190 ± 10 GPa, which make it very promising for interconnects of solid oxide fuel cells (SOFCs).

Numerical modelling of residual stresses during orthogonal cutting of Ti6Al4V using internally cooled cutting inserts

Residual stress has an adverse effect on the fatigue strength of machined components. The parts used in high end industries like aerospace and automobile sector needs to be carefully examined for the residual stress development during machining process. In this paper, both thermal and mechanical effects have been taken into account to predict the residual stress in workpiece while machining using internal cooled cutting inserts. The internal cooling system has now a days being used as an advanced cooling system for Ti and Ni based materials. In the present paper, Oxley’s model for slip line theory and contact theory using McDowell’s hybrid method have been used to predict the forces and residual stress respectively. The effect of change in the flow of lubricant from laminar to turbulent in internal channel of cutting insert has also been analysed. It has been found analytically that the cutting force of 761 N during dry turning is decreased to 511 N and 494 N in case of laminar and turbulent flow respectively. Besides this, the generation of compressive residual stress is found at the surface layer of machined specimen for internally cooled cutting inserts. The maximum compressive stress of 150 MPa at 0.03 mm depth of work piece has been found in case of laminar flow and 100 MPa for the turbulent flow.

Study of the degradation of a fine-grained YSZ–NiO anode material during reduction in hydrogen and reoxidation in air

In this work, the high-temperature reduction of nickel oxide and reoxidation of metallic nickel in the YSZ–NiO anode material have been studied. As-sintered material (of mode 1) manufactured by tape casting underwent two treatment modes: one-time reduction (mode 2) in pure hydrogen for 4 h at 600 °C under a pressure of 0.15 MPa; reduction/oxidation (redox) for five cycles in hydrogen/air atmospheres at 600 °C (mode 3). The material of mode 1 exhibited a bending strength of about 209 MPa. This level is high enough for anode materials. Significant changes have been detected in the microstructure of the material reduced in hydrogen (mode 2). Agglomerates of particles (average size about 5 µm) with a predominance of the zirconium phase as well as regions of small particles (1 µm) with uniformly distributed both the nickel and zirconium phases were revealed. The intergranular fracture micromechanism prevailed in the specimens tested. The material strength (40 MPa) did not satisfy the requirements for anode materials. Despite too “rigid” redox treatment mode in pure hydrogen and air at 600 °C (mode 3), the cermet is not inferior in strength (85 MPa) to those fabricated using other techniques. On the specimen fracture surface, a porous core and dense outer layers have been revealed. An increased amount of nickel in the surface layer is probably a consequence of the microstructural transformation due to the diffusion of nickel from the subsurface region towards the surface. The redox treatment caused the specimen core degradation due to forming large pores, their coalescence into cracks, and loss of material integrity. In contrast to the mixed fracture micromechanism noted in the specimen surface layer, the intergranular one in the core was revealed. The reached level of electrical conductivity and a positive effect of the treatment on the material strength indicate the potential of the tape cast material, especially, in the case of reduction in Ar–5 vol% H2 gas mixture instead of pure hydrogen.

Mechanisms of self-organization in tribosystems operating under conditions of abnormally low friction and wear

The article presents theoretical and experimental studies of tribosystems operating under conditions of normal and abnormally low friction and wear when changing the external conditions of their operation. A comparative analysis of self-organization mechanisms of tribosystem operating under conditions of normal mechanochemical and abnormally low friction and wear is performed to determine the conditions of transition to such a mode. There was determined another possible way of converting tribosystems to conditions of abnormally low friction and wear by modifying the surface layer of bronze specimens using finishing treatment with the use of a mineral of amphiboles (jade) group.

The Thermal Load and Ablation Mechanism of Piston Subjected to Detonation

Abstract The piston in reciprocating engine would be badly ablated under severe knock. However, the mechanism of the detonation-induced thermal ablation of piston is still unclear. A detonation bomb device (DBD) was used to measure the thermal load of piston under detonation. A test specimen mounted on the detonation bomb acts as a piston to bear the detonation load. Transient thermal numerical analysis was performed using the finite element method. Temperature of the specimen and in-cylinder pressure were collected synchronously. A method for estimating wall heat flux under detonation was proposed. Results showed that the heat received by the specimen accounts for about 20.9% of the total heat released by the mixture in this research. Under continuous detonations, the heat of the surface layer could not be conducted to the interior in a short time, leading to a rapid rise in surface temperature. The overall temperature rise of the specimen limits the heat dissipation of the specimen surface layer, resulting in the specimen being ablated by the over-temperature and over-pressure. Piston thermal ablation by detonation is verified and reappeared in the detonation bomb. The thermal load of the piston is largest under theoretical equivalent ratio.

Research on Mechanical Properties of 210Cr12 Shaft Surface Processed with Rolling

The rolling process is one of the most effective ways for strengthening a part’s surface. As the press force exerted on specimen in rolling process, material in the surface layer will deform plastically if the press force is sufficient. That might result in grain refinement, dislocation configuration change, or phase change in specimen surface layer material. Consequently, the surface material mechanical properties can be changed. The effects of rolling parameters on surface residual stress, micro-hardness, and surface roughness for a 210Cr12 shaft have been investigated. After the rolling process, the surface residual stress of the specimen changes from tensile stress to compressive stress, and a stable residual compressive stress layer is formed. The maximum absolute value of compressive stress can be up to 216MPa. With the increase of the value of contact stress exerted on shaft surface and the number of rolling cycles, the absolute value of residual compressive stress increases firstly and then becomes stable. With the increase of depth from shaft surface to interior, the absolute value of residual compressive stress increases initially, then decreases and disappears finally. The maximum absolute value of residual compressive stress exists at the position beneath specimen surface about 0.025mm. The depth of residual stress layer is about 0.2 mm. Research results indicate that shaft surface microhardness can be improved within small range, surface roughness can be reduced up to 67%.

Carbonation of Portland-Zeolite and geopolymer well-cement composites under geologic CO2 sequestration conditions

Degradation of Portland cement under supercritical CO2 conditions (scCO2) is one of the major concern in geological sequestration projects. This paper presents the research on two novel types of binders considered to display a CO2 corrosion resistance potential: (1) Portland cement partially replaced with 20, 30 and 40 wt % of zeolite and blended with Styrene-Butadiene (SB) Latex and (2) geopolymer based on lime-slag and lime-pozzolan blends. Specimens were placed in an autoclave, covered with water, heated up to 100 °C and pressurized with 7 MPa CO2 in order to simulate CO2 environment in the Croatian wellbore. On behalf of tests on compressive strength, porosity, permeability and alkalinity, as well as thermogravimetry, X-ray diffraction and SEM microstructural analyses of samples at various penetration depths, carbonation mechanisms were discussed. Portland-Zeolite composites have been argued as potential CO2 resistant cement systems, with an replacement rate below the minimally tested addition of 20 wt %, as excessive replacement rates resulted in an increase in porosity and permeability. Geopolymer composites based on lime activation unfortunately haven't exhibited required properties for application in well cementing of CO2 injection wells. Calcium carbonate polymorphs precipitated throughout the whole specimen thickness of all samples, but preferably in mixtures based on Ca-richer raw materials. A re-precipitation of calcium carbonate filled in the porosity preferentially at the 0.5 mm surface layer of PC-based specimens, due to the outward diffusion of calcium at the early stage of carbonation.

Effect of ultrasonic surface rolling on surface layer properties and fretting wear properties of titanium alloy Ti5Al4Mo6V2Nb1Fe

This article investigated the effect of different ultrasonic surface rolling (USR) processing parameters on microstructure, surface layer properties, and fretting wear properties of a kind of high strength and high toughness titanium alloy Ti5Al4Mo6V2Nb1Fe. With the aid of SEM, TEM, EDS, and 3D-profile scanning, the surface layer of specimens was characterized and analyzed. The experimental results showed that the severe plastic deformation took place on the specimen surface layer. The thickness of plastic deformation layer could reach more than 230 μm. The grains in the surface layer were refined, which was induced by dislocations of high density, such as dislocation tangles and dislocation walls. The surface layer properties were improved compared with untreated specimen: the surface roughness decreased from 0.18 μm of untreated specimen to 0.06 μm; the microhardness of surface increased about 20%; the compressive residual stress about −1000 MPa occurred. The wear rate reduced about 70% after USR and the fretting wear resistance was improved.

The influence of grinding wheel type on microhardness and residual stresses in vacuum-carburised 20MnCr5 steel using the single-piece flow method

The aim of the experiment described in the paper was to determine the effect of selected conditions of abrasive machining on the size and distribution of microhardness and residual stresses developed in the technological surface layer of flat specimens made of 20MnCr5 steel. The specimens were subjected to single-piece flow low-pressure carburising (LPC) and high-pressure gas quenching (HPGQ) in a 4D Quenching chamber in order to achieve an effective case depth of ECD=0.4 mm. This was followed by grinding the specimens with Quantum and Vortex alumina grinding wheels. Cooling and lubricating fluid were supplied to the grinding zone using the flood (WET) method. The samples were ground in one pass of the grinding wheel using one grinding depth (ae = 0.01 mm). The measurements for each specimen were made twice - after the thermo-chemical treatment and after the grinding. Microhardness and residual stress were measured using the X-ray method sin2Ψ. The final part of the article provides an analysis of the measurement results and presents conclusions and recommendations for further studies.

STRENGTH CHARACTERISTICS OF HYPEREUTECTIC SILUMIN AFTER ELECTRON BEAM MODIFICATION

Irradiation (SOLO installation, Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences) of hypereutectic silumin specimens of Al-(22-24)Si composition with an intense pulsed electron beam was carried out. The formation of the structure of highspeed cellular crystallization of aluminum (cell size 250-600 nm) was revealed. It was shown that the cell boundaries are strengthened by globular-shaped silicon particles (particles of size 50-70 nm). It was found that the hardness of the silumin specimen surface layer increases by more than 5 times after modification. Tensile tests of plane proportional samples showed an increase in the ductility of irradiated samples while maintaining the tensile strength.

The Effect of Hydrogen on Martensite Transformations and the State of Hydrogen Atoms in Binary TiNi-Based Alloy with Different Grain Sizes.

The analysis presented here shows that in B2-phase of Ti49.1Ni50.9 (at%) alloy, hydrogenation with further aging at room temperature decreases the temperatures of martensite transformations and then causes their suppression, due to hydrogen diffusion from the surface layer of specimens deep into its bulk. When hydrogen is charged, it first suppresses the transformations B2↔B19′ and R↔B19′ in the surface layer, and when its distribution over the volume becomes uniform, such transformations are suppressed throughout the material. The kinetics of hydrogen redistribution is determined by the hydrogen diffusion coefficient DH, which depends on the grain size. In nanocrystalline Ti49.1Ni50.9 (at%) specimens, DH is three times greater than its value in coarse-grained ones, which is likely due to the larger free volume and larger contribution of hydrogen diffusion along grain boundaries in the nanocrystalline material. According to thermal desorption spectroscopy, two states of hydrogen atoms with low and high activation energies of desorption exist in freshly hydrogenated Ti49.1Ni50.9 (at%) alloy irrespective of the grain size. On aging at room temperature, the low-energy states disappear entirely. Estimates by the Kissinger method are presented for the binding energy of hydrogen in the two states, and the nature of these states in binary hydrogenated TiNi-based alloys is discussed.

Statistical Characteristics of Microplastic Strains of the Surface Layer of Austenitic Steel Under Monotonic and High-Cycle Loadings

The mechanical state of the surface layer of the studied metal is controlled by correlation between the ray energy of a coherent light source reflected from the surface of the metal polycrystal and the amplitude of microplastic strains of the elastically deformed surface, based on the analysis of statistical characteristics of the discrete brightness distribution of the image elements of the reflected ray. The regularities of the effect of mechanical loading on the statistical characteristics of the discrete strains distribution under elastic deformation of the surface layer of austenitic steel specimens are defined. An analysis of the sequence of correlation characteristics of the surface deformation defects allows one to reveal a linear dependence of the distribution of the discrete properties of the deformed surface relief on the load intensity factor. The obtained correlation characteristics show that with an increased load the brightness amplitude of the speckle pattern image elements drops due to the increase in the mean-square relief amplitude of the surface deformation defects. By analyzing statistical characteristics of the deformed surface of austenitic steel specimens, quantitative parameters of the descriptive statistics of scattered damage are defined. The regularities of the elastoplastic strain effect on the distribution of discrete surface deformations are obtained. A nonparametric evaluation of the loading intensity factor effect on the sequence of terms in series of mean-square sampled values of damage correlation characteristics under cyclic and static loadings, as well as the determination of strain amplitudes and loading durations as damaging factors during elastoplastic deformation of austenitic steel specimens, are performed.

ВИЗНАЧЕННЯ ВПЛИВУ МАТЕРІАЛУ ТА ХІМІКО-ТЕРМІЧНОЇ ОБРОБКИ НА ЗНОСОСТІЙКІСТЬ ЕЛЕМЕНТІВ УНІВЕРСАЛЬНО-ЗБІРНИХ ПЕРЕНАЛАГОДЖУВАНИХ ШТАМПІВ

The article presents the results of experimental studies of the wear resistance of metals in order to select the most effective for the manufacture of guide elements of prefabricated universal readjusted stamps. To determine the effect of the material and chemical-heat treatment of them on the wear resistance of the guide elements, the optimal friction pair was selected and tested under conditions similar to the operating conditions of the stamps. Specimens for testing were made in the form of cuts of steel 20, 12ХНЗА (12HNZA), 40Х (40Н) and 38ХМЮА (38HMYUA). Laboratory tests were performed on the machine MИ-1M (МI-1M) under a load of 50, 75 and 100 kgf with a contact area of 243 mm2. The amount of wear was determined by the gravimetric method of I. Kragelsky. Before testing for wear resistance, the specimens were subjected to thermal and heat-chemical treatment: Steel 20 (cementation, normalization, quenching, tempering), 12ХНЗА (12HNZA) (cementation, high tempering, quenching, tempering), 40X (40Н) (quenching, tempering, nitriding) and 38ХМЮА (38HMYUA) (quenching, vacation, nitriding). Studies of the microstructure and microhardness of the test specimens have shown that the nitriding of 38ХМЮА (38HMYUA) and 40X (40H) steel specimen reduces its wear by 1...2 µm and 2...3 µm, and the microhardness of both materials decreases by 50...100 Nm. The analysis of the wear intensity graphs on the number of cycles have shown that for all specimens there are two periods of wear (1 – running-in of rubbing surfaces, 2 – steady wear). Also, studies have shown that the surface layer of nitrated specimens on 38ХМЮА (38HMYUA) steel has a higher wear resistance and a slight tendency to seizing and hardening, providing a high resistance of the part to wear in various friction conditions. The results of testing samples under various loads have shown that the linear wear value is proportional to the change in the specific pressure value established on the basis of the conducted studies that the most effective material for the manufacture of guide elements for PURS is 38ХМЮА (38HMYUA) steel with the following thermal and heat-chemical treatment (quenching – 940 ... 950°C, tempering – 650°C and nitriding – 540°C).

Chloride Distribution Feature in Surface Layer of Cementitious-based Materials under Mere Cyclic Wetting and Drying Action

Chloride transport under wetting and drying environment is very complicated. A lot of research has reported maximum phenomena in chloride profiles under such environment. Considering the fact that most specimens in which chloride maximum was detected before either had inhomogeneous surface (might be influenced by skin effect) or were exposed to natural environment (might be influenced by rain washing), this study aims to reveal chloride distribution under mere wetting and drying condition in cement-based materials. The chloride distribution results in the surface layer of specimens with different water to binder ratio (W/B) detected by silver nitrate titration method (SNT), ion chromatography method (IC)and electric probe micro analysis (EPMA) present a fact that: maximum phenomena occur in all specimens under four wetting-drying regimes, no matter in paste or mortar, in free or total chloride, and whether with slag (SL) and fly ash (FA) or not. It suggests that mere wetting and drying action can incur chloride maximum phenomenon without the attendance of skin effect and rain washing, though sometimes confined by the accuracy of testing method, the position of maximum phenomenon can not be presented.

Long-term sulfate resistance of cementitious composites containing fine crumb rubber

This paper presents the results of a study on the effects of fine crumb rubber on the sulfate resistance of mortar mixtures. Mixtures with and without 10% silica fume (SF), containing 0%, 10% and 15% fine crumb rubber as a fine aggregate substitute material were subjected to sodium sulfate wet-dry cycles for two years. Changes in compressive strength, mass and longitudinal expansion of mortar bars were monitored. Micro computed tomography scan (CT-Scan) and scanning electron microscopy – energy dispersive spectroscopy (SEM – EDS) were also utilized in investigating specimen microstructure and degradation. Results indicate that while the SF was effective in resisting the expansion of mortar bars, the presence of crumb rubber in mixtures prepared without the SF led to a 52–57% reductions in longitudinal expansion relative to that of the plain reference mortar. Although SEM microstructural analyses suggest a higher preponderance of calcium silicate hydrate (C–S–H) intermixed with sulfate reaction phases and entrapped air voids in the outer surface layer of rubberized specimens, matrix cracking was significantly lower compared to the plain reference specimen. CT-Scan results also confirmed the severe degradation of the plain reference mortar specimen and the tendency of crumb rubber to increase the air void content of mortar mixtures. The enhanced resistance of rubberized mortar specimens prepared without the SF is traced to the selective growth of sulfate crystals in entrapped micro-sized air voids, and the proclivity of rubber particles to not only blunt cracks, but also predispose specimens to minimal cracking during deformation.

Features of the Surface and Subsurface Waves Application for Ultrasonic Evaluation of Physicomechanical Properties of Solids. Part 2. Strenghtned Inhomogeneous Surface Layer

The propagation of a pulsed signal of a surface wave over an object with a non-uniform surface layer, obtained, for example, as a result of surface hardening, with structural damage, is accompanied by the dispersion of the velocity of the wave carrying important information about the parameters of such a layer. The aim of the work is to study the relationship between the acoustic parameters of a pulsed acoustic signal of a surface and subsurface waves and the surface layer of steel specimens hardened by high-frequency hardening, and gray iron-chill. Features of the surface and subsurface waves application for ultrasonic evaluation of physicomechanical properties of solids. Strenghtned inhomogeneous surface layer.A brief analysis of the known works on determining the depth of hardened surface layers by various methods, including high-frequency hardening, cementation, etc., is carried out. Based on the Oulder integral expression. The dependence connecting the wave velocity, its frequency, the depth of the hardened layer and the spatial distribution of hardness represented as a step with a changing slope of its side surface simulating the transition zone of the hardened layer are calculated.Using the pulse method and low-aperture transducers with a frequency of 1−3.8 MHz, the dependences of the surface wave velocity on the cutting height of a layer hardened by HDTV hardening are obtained. A comparison of experimental data and calculations of the theoretical model showed a good qualitative correspondence between them, demonstrate a high «sensitivity» of the method in relation to the nature of the change in hardness over the depth of the hardened layer. It is shown that the proposed approach is promising for solving the inverse problem of restoring the spatial distribution of hardness based on experimental data.The goniometric method was approbated to determine the dependence between amplitude-angle characteristics and depth of the surface steel layers hardened by high-frequency hardening and depth of hardened gray iron specimens layer – with chill. It is shown that the optimal angle corresponding maximum of excited surface wave amplitude in steel specimens is decreasing up to 24–26'vs. hardened depth layer. But when the tested specimens from cast iron this angle decreasing is nearly of 6°. Recommendations on the use of research results in practice are given.